Aplicaciones de Valvulas de Expansion Electronic As y Ventajas Por Fernando Becerra

D A N F O S S F O O D R E T A I L 17/06/2011 / 1

MAKING MODERN LIVING POSSIBLE

Válvulas de Expansión Electrónicas

Danfoss Refrigeration

RefriAmericas Medellin Junio 2011


OPCIONES DE AHORRO DE ENERGIA

EN APLICASIONES DE REFRIGERACIÓN

1. Selección adecuado de Intercambiadores de calor.

2. Válvulas de expansión electrónicas.

3. Dimensionamiento de tuberías.

4. Elección adecuada del refrigerante.

5. Opciones de compresores de alta eficiencia.

6. Compresión en paralelo.

7. Sistema de control.

8. Variador de frecuencia en compresores y condensadores.

9. Sistemas en paralelo con variador de frecuencia.


CONSUMO TIPICO DE ENERGIA EN UN SUPERMERCADO

COMPRESSORES

30%

VENTILADORES DOS

CONDENSADORES

4%BALCÕES FRIGORÍCOS

16%

INTERNA

21%

EXTERNA

4%

SALAS DE PREPAROS

8%

DIVERSOS

6%

VENTILADORES

4%

AR CONDICIONADO

7%

REFRIGERACIONILUMINACION

OTROS

AIRE CONDICIONADO


CONSUMO TIPICO DE ENERGIA EN UN CUARTO FRIO

SH afectan el COP

del compresor


Heat

Pre

ssu

re

Enthalpy

A’

B

AE

D

C C’

Condensing temperature

Out temperature

Room temperature

Evaporating temperature

Dtcond.

Dtevap.

PRESION DE EVAPORACION Y CONDENSACION


UNIDADES CONDENSADORAS ENFRIADAS POR AIRE

Tcond. = Tamb. + 15°C


CUANTO PAGAMOS POR UNCONDENSADOR PEQUEÑO?

T cond = 45°C

Tevap= - 5°C

COP1 = 2,39

T amb = 25°C

T cuarto = 2°C

MT 100 (9 HP)

R22

Q comp. = 7,2 KW

Tcond = 40°C, T evap = - 5°C

Costo $ /mes = 7,2 KW x 18 horas x 30 días/mes x 400 $/KWH = 1.550.000 $ /mes

COP1/COP2 = 12,5%, = $ 190.000 / mes!

$ 2.300.000 al año

T cond = 40°C

Tevap= - 5°CSC=4, SH=5/8

COP2 = 2,73


Tevap. = Tcuarto – 6 ó 10 °C

EVAPORADORES ALETADOS


CUANTO PAGAMOS POR UNEVAPORADOR PEQUEÑO?

T cond = 40°C

Tevap= - 10°C

COP1 = 2,29

T amb = 25°C

MT 100 (9 HP)

R22

T cuarto = 2°C

Q comp. = 7,2 KW

Tcond = 40°C, T evap = - 5°C

COP1/COP2 = 16% = $ 248.000 / mes!

$ 3.000.000 /año

T cond = 40°C

Tevap= - 5°C

COP2 = 2,73


Super Heat:

Diferencia entre la temperatura

de succión y la temperatura de

evaporación o saturación.

SH

CONTROL SOBRECALENTAMIENTO SH


SOBRECALENTAMIENTO TOTAL

SH 2 SH 1

SH 1 + SH 2 20°C

SH 1 = 5°C, válvula de Expansión

SH2 Aislamiento.


Function of TXV-TE… – SH control

Charges:

Universal MOP

(ballast)

Adsorption

Tcharge -> Pcharge

Pcharge x Adiaphragm = (Pevaporator x Adiaphragm) + Fspring

D A N F O S S F O O D R E T A I L / 13

5 6 8 10 12 1686

88

90

92

94

96

98

100

5 6 8 10 12 16

INDEX

SUPERHEAT ( S2-S1)

RELATIVE COP

“COP vs SH”


Injection Control – Superheat

• Large superheat => Low evaporation Temperature => High energy consumption

Air temperature

Refrigerant

temperature

No superheat

Small superheat

Large superheat

Te

mp

era

ture

Position

S3

S4

S2Po

Po

Po

Inlet Outlet

S5

S4

S3

S2

PoS1


TEMP. Cuarto Frio = + 2°C

TEMP. Cuarto Frio = + 2°C

T evap. = - 5°C

T evap. = - 10°C

Por cada 1°C que varíe el SH,

la temperatura de succión varia 1°C.

COP1 = 2,73 (óptimo), 7,2 Kw.

COP2 = 2,28 (evap. sin llenar)

SH 1 = 5°CSH 2 = 3°C

SH 1 = 10°CSH 2 = 3°C

COP2/COP1 = 17% más de consumo de energía.

17% = $ 264.000 / mes.

$ 3.150.000 / año

7,2Kw x 400 $/Kw x 18 h/día x 30 días/mes = $ 1.550.000 / mes


Tcond = 40°C, T cuarto frio = + 2°C, mismo evaporador, MT 100.

T evap. = - 5°C

T evap. = - 5°C

COP1 = 2,73 (óptimo)Q comp = 7,2 Kw

COP3 = 2,58 (succión mal aislada)

SH 1 = 5°CSH 2 = 3°C

SH 1 = 5°CSH 2 = 15°C

COP3/COP1 = 6%

7,2Kw x 400 $/Kw x 18 h/dia x 30 dias/mes = $ 1.550.000 / mes

6% = $ 93.000 / mes.

$ 1.000.000 / año

CUANTO PAGAMOS POR ALTOS SH?


EXPANSION TERMOSTATICA vs ELECTRONICA


EXPANSION TERMOSTATICA vs ELECTRONICA

+ Rápida

+ Segura, retornos de líquido

Maneja variaciones de carga altas 90%

Maneja SH estables

Ahorro de energía

Posibilidad de intercambiar orificios

Misma válvula para todos los refrigerantes

Un controlador puede manejar varias válvulas

Precisión en la lectura de los sensores

Menos problema con ubicación de sensores

No ajustes manuales

No hay problemas con variaciones de Pcond.

Opera como solenoide.

Bajo costo inicial

Fácil selección y manejo técnico

Posibilidad de intercambio de orificios

Instalación sencilla

Maneja variaciones de cargas máx. 20%


1. VALVULAS ELECTRONICAS MODULANTES


AKV Valve

• PWM Principle (Pulse Width Modulating)

AKV closed0 6 12 seconds

AKV Open

Periode time (PT) = 6 seconds

OD % =OT x 100

PTOT = Opening Time.

AK

V O

D %

TimeHomework

Intro

Temp. control

Injection

AKV valve

Defrost

Ctrl. types

Next session

2. DX ELECTRONICA PULSANTE


AKV electronic expansion valves

Pulse width modulated

Integrated solenoid functionExchangeable orificesWide capacity rangeAll refrigerantsHydraulic damping systemCoil program

AKV 10AKV 20

AKV 15


7 CAPACITY STEP

FLARE/SOLDER VERSION

PARTSPROGRAMME

Coil: 2.5 - 5 and 8 meter cable

WIDE TEMP. RANGE

230 - 24 V AC AND DC

18F COIL PRINCIPPLE

ALL REFRIGERANTS

AMMONIA VERSION

SEMIHERMETIC DESIGN

AKV electronic expansion valves


AKV 15


AKV capacity range

5

10

15

20

1 2 3 4 5 6 7

R22 C

apacity in k

W

Orifice no.

1

1,62,54

6,3

10

16

25

50

75

100

1 2 3

25

40

100

AKV 10 AKV 15

200

1 2 3 4 5

100160

250

400

630

AKV 20

400

600

800

63

4


CONTROLADORES DX ELECTRONICA

EKC 315AAKC 24P / P2

PARA TODOS LOS REFRIGERANTES

AKV/A AKV/A


CONTROLADORES DX ELECTRONICA

PARA TODOS LOS REFRIGERANTES

AKV/A AKV/A


AHORRO DE ENERGIA CON DX ELECTRONICA

7,2Kw x 400 $/Kw x 18 h/día x 30 días/mes = $ 1.550.000 / mes

23,2% = $ 360.000 / mes

15% = 230.000 / mes

$ 2.760.000 / año


How do measure superheat?

Evaporator

Surface temperature: S5

Refrigerant

temperature S1

Pressure Po

Air on temperature

S3

Air of temperature

S4

Refrigerant

temperature S2

One measurement to much on refrigerant side...


• Po [°C] is equal to S1

S5

S4

S3

S2

PoS1

S2S1

Po

S2S1

PoPo [°C] is not equal to S1,

superheat = S2-Po[°C]

How do measure superheat?



5K

S2

Temp.

°C

S1 S2

AKS32R

AKS32R (Te)

Comparison of two ways of measuring the superheat signal:SH = S2 - S1 or SH = S2 – Te (true value)(Te must be calculated from a Pe measurement)



5K

7K

S2

AKS32R (Te)

Temp.

°C

S1 S2

AKS32R

Comparison of two ways of measuring the superheat signal:SH = S2 - S1 (bad measure)SH = S2 – Te (true value)(Te must be calculated from a Pe measurement)


Pressure Transmitter advantage

• Po is a better measurement than S1 and is used/required in newest controller versions

S5

S4

S3

S2

PoS1


Porque DX electrónica ahorra energía?

Adaptive superheat control


S2-To

Length

MSS start

Stable Unstable Stable

S2

To

Injection function


3 2 1

Minimum stable superheat =>

Best evaporator performance

1

2

3

Minimum stable superheat - Theory

When an evaporator is “under filled” with refrigerant, the superheat signal is high and very stable at the outlet of the evaporator. Only a small area of the evaporator is utilised => degraded performance.

When the evaporator is almost full, liquid drops of refrigerant will be present at the outlet of the evaporator and this will result in an unstable superheat signal. This will result in control hunting problems => degraded performance.

If the evaporator is “over filled” with refrigerant, liquid will flow back into the suction line => Degraded system performance + risk of damaging the compressor. The superheat signal will be very stable at 0K.


86

88

90

92

94

96

98

100

5 6 8 10 12 16

MSS curve Relative COP

Superheat

Minimum stable superheat - Theory

The superheat is reduced until the signal becomes unstable.

Then superheat is increased a bit until stability is found

followed by a new reduction and so on!

It happen in all conditions.


Injection Control – Electronic valve

Superheat

Q0

Lo

ad

ran

ge f

or

the e

vap

ora

tor

MSS = f (Q0,T0 etc.)

Unstable zone

Stable zone

Adaptive valve

Homework

Intro

Temp. control

Injection

AKV valve

Defrost

Ctrl. types

Next session


The adaptive superheat for the Danfoss

controller enables extra savings

compared to other suppliers.

Adaptive vs. Fixed superheat control

• Other suppliers are often using a fixed set point for the control of the evaporator superheat.

• In theory this means that the evaporator can be fully utilised in one operation point, but this would require a very time consuming manual adjustment of the set point which is never carried out in praxis.

• A fixed superheat control algorithm will not detect when liquid is present at the evaporator outlet. Hence the superheat set point must be set in a “safe” distance from the minimum stable superheat in order to ensure that liquid will not flow back into the suction line.

Other suppliers



• The measuring accuracy of the evaporating pressure and the gas outlet temp. must be very accurate in order to control superheat at low values.

• Competitors often use low cost and thereby low precision pressure transmitters.

• The result is that the superheat set point has to be set a quite high value in order to eliminate the risk of having liquid flow back to the suction line due to lousy measuring accuracy.

• The result is of course even higher savings with the Danfoss adaptive control of superheat.


Saving example:

MT100 (9 HP hermetic):7,2Kw x 400 $/Kw x 18 h/dia x 30 dias/mes =

$ 1.550.000 / mes

9% = $ 140.000 / mes.

$ 1.680.000 / año

Medium sized supermarket with 3

compressor MT100:

Save energy: $ 420.000 / mes

Total $ 5.040.000 / year


• The adaptive superheat control will typically obtain a 2-3 K lower superheat reference than with a competitor fixed superheat reference.

• By lowering the superheat, the suction pressure can be increased by approx. the same amount. The energy savings by increasing suction pressure by 1K is typically 3 %.

• So the energy savings by using Danfoss adaptive superheat control will typically be 6-9 % compared to a fixed superheat control.


Aplicaciones:

• Instalaciones con variaciones de cargas térmicas

• Instalaciones con variación de presión de condensación

• Túneles de congelación

• Intercambiadores de placas

• Intercambiadores con variación de carga (caudal, diferencial temp.)

• Equipos que requieran protección y precisión


How to select the right size AKV



1. Find evaporator capacity

2. Calculate pressure drop across AKV

3. Correct for sub-cooling

4. Correct capacity to pull-down capability

5. Select correct AKV size

6. Determine correct liquid line dimension



1. Find evaporator capacity



2. Calculate pressure drop across AKV



3. Correct for sub-cooling



4. Correct capacity to pull-down capability



5. Select correct AKV size



6. Determine correct liquid line dimension


Questions

Documents

Aplicaciones de Valvulas de Expansion Electronic As y Ventajas Por Fernando Becerra